Conventionally, an organic compound-based ultraviolet absorber, an inorganic compound-based ultraviolet-shielding agent or the like is blended in cosmetic compositions having a capability of ultraviolet protection. The organic compound-based ultraviolet absorber now on use includes 2-ethylhexyl p-methoxycinnamate for UVB protection and 4-tert-butyl-4′-methoxydibenzoylmethane for UVA protection. However, when these are blended in a large amount so as to enhance the capability of ultraviolet protection, a problem of increase in stickiness or skin irritation arises. Furthermore, 4-tert-butyl-4′-methoxydibenzoylmethane and the like cannot be stably blended because of their low solubility in an oil agent and coloration due to chelation with metal ion. In addition, these UV absorbers are poor in the photostability and their decomposition jeopardize the safety.
On the other hand, with increasing attention to the safety of cosmetics, use of an inorganic compound-based ultraviolet-shielding agent is widespread and in particular, titanium oxide and zinc oxide are used for general purposes. However, if titanium oxide is blended in a high proportion so as to obtain sufficiently high protection against ultraviolet rays, dry or powdery feeling is generated and when applied to skin, unpleasant whitening seriously occurs. As compared with titanium oxide, zinc oxide is low in the capability of ultraviolet protection per unit mass despite its excellent transparency and therefore, for obtaining sufficiently high ultraviolet protection, zinc oxide must be blended in a higher proportion than titanium oxide, as a result, dry or powdery feeling is generated and moreover, aggregation/gelling takes place due to the elution of zinc ion.
These inorganic compound-based ultraviolet-shielding agents have photocatalytic activity and therefore, are surface-treated with silica, alumina or the like, however, the concealing effect is insufficient and other cosmetic base materials including an organic compound-based ultraviolet absorber are decomposed.
As such, the kind and the blending amount of the ultraviolet-protecting agent which can be blended in cosmetic compositions for preventing sunburn are limited and a fully satisfactory ultraviolet-protecting agent has not been found.